We shall find that the economic relations constitute a machinery by which men devote their energies to the immediate accomplishment of each other’s purposes in order to secure the ultimate accomplishment of their own, irrespective of what those purposes of their own may be, and therefore irrespective of the egoistic or altruistic nature of the motives which dictate them and which stimulate efforts to accomplish them.In other words, economics is about choices in a world where you can't have everything at once. As Thomas Sowell says, it's the study of the allocation of scarce resources with alternative uses. They aren't all material resources; sometimes they're measured in the time or effort available in our lives, always a finite quantity.
In this sense of a "market," people make choices and trade-offs. The point is not to reduce every trade-off to a monetary one, but to let the choices be made by each person rather than by a distant, crowned bureaucrat.
H/t Maggie's Farm.